Documentation comments for both Python and Rust

[probablySophie]

Someone asked in the Matrix chat yesterday about documentation comments in Python🐍. And I accidentally learned how tree-sitter syntax highlighting works to get doc comments working.
While I was there I figured I may as well do it for Rust🦀 too!

---

Rust documentation comments are

/// this is a documentation comment

and have the tree-sitter scopes:
["source_file", "impl_item", "declaration_list", "line_comment", "doc_comment"]

So adding a search for line_comments that contain doc_comments lets us isolate them and then themes can target @comment.documentation

---

Python documentation comments are

"""
   This is a documentation comment (and also a valid string)
"""

Tree-Sitter scopes:
["module", "expression_statement", "string", "string_content"]

Because the doc comments are also valid strings the suggested code looks for expression_statements that contain strings and that start with """.

Regular """ strings aren't affected because they're assignment > string instead of expression_statement > string

---

Thank you! 😃

[archseer]

@the-mikedavis wow, I guess we don't need grammar changes to detect this?

[the-mikedavis]

It looks like python exposes a (string_start) node under (string) which contains these markers anyways, but it is handy that we wouldn't necessarily need the python grammar to do that in order to match this. (@probablySophie you can use :tree-sitter-subtree when selecting a syntax node to see how the nodes are laid out - this is usually more helpful than :tree-sitter-scopes which only shows the node names.)

I think we should follow nvim-treesitter's queries for this instead though since they're more specific and don't need #match? or #eq? at all: https://github.com/nvim-treesitter/nvim-treesitter/blob/dfd3207ed43a0c572c13acc02bf9d7dc270f4030/queries/python/highlights.scm#L201-L222